First principles calculation within density functional theory (DFT) has been used to calculate the structural, electronic and optical of ZnSiP2 chalcopyrite semiconductor. The result of band structure, total density of state (DOS) and partial density of state (PDOS) have been discussed. The dielectric constant, refractive index, reflectivity, absorption coefficients and loss function have been presented in energy range of 0-25 eV. The calculated values of these parameters are in good agreement with the experimental values and the value reported by previous researchers.